A new snapping shrimp of the Alpheus armatus Rathbun, 1901 species complex, Alpheus rudolphi spec. nov., is described based on a single female holotype collected off Alagoas, northeastern Brazil (09°55.11’S 35°32.73’W). The new species differs from all other species of the A. armatus complex by the unique configuration of the orbito-rostral region of the carapace.